How long should you work on your art in one sitting? Is it OK to do it without resting or should you take a break after a certain period of time?

Although when inspiration strikes, we all can work long hours without even noticing how the time flies, I think it's best to do a short break every 30-45 minutes of work. Your brain is very active when you create and it's best to take a rest so that you would feel the mental and physical energy renewed.

About 5-10 minutes of rest usually is enough. During this period go drink a glass of water, stretch, or take a short walk. In 10 minutes you can come back to your art and work some more if you want.